This paper investigates the temporal behaviour of open-circuit bright photovoltaic spatial solitons by using numerical techniques. It shows that when the intensity ratio of the soliton, the ratio between the soliton peak intensity and the dark irradiance, is small, the quasi-steady-state soliton width decreases monotonically with the increase of τ-, where τ- is the parameter correlated with the time, that when the intensity ratio of the soliton is big, the quasi-steady-state soliton width decreases with the increase of τ- and then increases with τ, and that the formation time of the steady-state solitons is not correlated with the intensity ratio of the soliton. It finds that the local nonlinear effect increases with the photovoltaic field, which behaves as that the width of soliton beams is small and the self-focusing quasi-period is short. On the other hand, we also discuss that both the time and the temperature have an effect on the beam bending.
We theoretically study the evolution of dark solitons in the biased photorefractive-photovoltaic crystal by using beam propagation method(BPM). We find that when the absolute value of the extra bias field is less than the photovoltaic field, the dark screening-photovoltaic(SP) solitons can be observed. The initial width of the dark notch at the entrance face of the crystal is a key parameter for generating an sequence of dark coherent solitons. If the initial width of the dark notch is small, only a fundamental soliton or Y-junction soliton pair is generated. When the initial width of the dark notch is increased, the dark notch tends to split into an odd(or even) number of multiple dark solitons, which r ealizes a progressive transition from the low-order solitons to a sequence of higher-order solitons.
We study two families of two-dimensional bright lattice solitons in photovoltaic-photorefractive crystals.It is shown that self-focusing and self-defocusing lattice solitons are possible only when their power level exceeds a critical threshold.It is found that self-focusing lattice solitons exist not only in the semi-infinite band gap,but also in the first band gap,whereas self-defocusing lattice solitons exist only in the first band gap.The structures of these lattice solitons are also analyzed.Our results indicate that a self-focusing lattice soliton in the semi-infinite band gap is more confined than in the first band gap so its tails in the first band gap occupy many lattice sites;when a self-defocusing lattice soliton is close to the second band,the self-defocusing lattice soliton is more confined so its tails occupy a few lattice sites.
This paper studies numerically the dark incoherent spatial solitons propagating in logarithmically saturable nonlinear media by using a coherent density approach and a split-step Fourier approach for the first time. Under odd and even initial conditions, a soliton triplet and a doublet are obtained respectively for given parameters. Simultaneously, coherence properties associated with the soliton triplet and doublet are discussed. In addition, if the values of the parameters are properly chosen, five and four splittings from the input dark incoherent spatial solitons can also form. Lastly, the grayness of the soliton triplet and that of the doublet are studied, in detail.
